Patent GB-889949-A (GB)
Title: Process for the purification of sugar
IPC: C13B20/14
Filed: 1958-05-19
Abstract: 889,949. Purifying saccharine liquids. ROHM & HAAS CO. May 19, 1958 [June 5, 1957; Jan. 6, 1958 (2)], No. 16044/58. Class 127. [Also in Group I] The purity of sugar in a solution contaminated with organic impurities derived from the natural source of the sugar is improved by (A) passing the sugar solution through a bed of ion-exchange resin particles which are in the salt form at least in that half of the bed which extends interiorly from the effluent end, substantially the remainder of the resin particles in that portion of the bed which extends interiorly from the influent end, preferably the uppermost quarter, having a different form of exchangeable ions such as are derivable from a regeneration treatment with a solution of a non-salt electrolyte; (B) passing water through the bed to remove sugar therefrom; and (C) collecting a selected effluent fraction which contains a higher ratio of sugar to organic impurities than does the feed solution; when the cycle of operations is repeated continuously; (D) regenerant is passed through the bed to regenerate only those particles in the portion of the bed which enters interiorly from the influent end (as mentioned above); and (E) water is then passed through the bed to remove salts liberated by the regenerant. The bed may contain cation-exchange resin particles, e.g. of the sulphonic acid type in the sodium form, which are in the hydrogen form towards the influent end or anion-exchange resin particles, e.g. of the quaternary ammonium type in the chloride form, which are in the hydroxide form towards the influent end. The purified sugar effluent obtained by the treatment is brought to a pH within the range 5 to 9 generally desired for maximum separation of the sugar by adding to the effluent an appropriate non-salt electrolyte, by passing the effluent through a bed of a weakly basic anion-exchange resin in the hydroxide form or, as appropriate, a weakly acidic cation-exchange resin in the hydrogen form, or by combining the selected sugar-containing effluent fractions from separate cationexchange and anion-exchange treatments whereby there results a mixture of the required pH, as depicted diagrammatically in Figs. 3A and 3B, and Fig. 2 respectively (not shown), the effluent is concentrated while at this pH and then the sugar is crystallized out; impure sugar liquor untreated by the ion-exchange treatment may be added to the effluent prior to the crystallization. The volume of sugar solution passed through the bed is from 5 to 35% of the bed volume and the volume of water subsequently passed through the bed is from 1 to 4 times the volume of sugar solution previously passed through. An effluent fraction neither high nor low in sugar relative to the organic impurities may be recycled. The treatment may be applied to diluted molasses from various sources. Fig. 13 depicts a continuous processing plant for the purification of sugar liquor incorporating an ion-exchange column 27 in accordance with the invention. There are disclosed eighteen specific examples. Specifications 577,707 and 654,706 are referred to.